U.S. patent application number 13/121328 was filed with the patent office on 2011-07-28 for suction sheet.
This patent application is currently assigned to NITTO DENKO CORPORATION. Invention is credited to Toshimitsu Tachibana.
Application Number | 20110183108 13/121328 |
Document ID | / |
Family ID | 42059784 |
Filed Date | 2011-07-28 |
United States Patent
Application |
20110183108 |
Kind Code |
A1 |
Tachibana; Toshimitsu |
July 28, 2011 |
SUCTION SHEET
Abstract
A suction sheet (1) to be attached onto a suction surface (4a)
of a suction apparatus (4) that holds an object by vacuum suction
is provided with a substrate (2) and a porous body (3). The
substrate (2) has one surface (2a) and the other surface (2b), and
the one surface (2a) is brought into contact with the suction
surface (4a). Further, a plurality of through holes (21) are
provided in the substrate (2). The porous body (3) has a thickness
of 1.4 mm or less, and is adhered onto the other surface (2b) of
the substrate (2) so as to cover the through holes (21).
Inventors: |
Tachibana; Toshimitsu;
(Osaka, JP) |
Assignee: |
NITTO DENKO CORPORATION
Ibaraki-shi, Osaka
JP
|
Family ID: |
42059784 |
Appl. No.: |
13/121328 |
Filed: |
September 25, 2009 |
PCT Filed: |
September 25, 2009 |
PCT NO: |
PCT/JP2009/066656 |
371 Date: |
March 28, 2011 |
Current U.S.
Class: |
428/131 |
Current CPC
Class: |
B32B 2250/24 20130101;
B32B 2264/0257 20130101; B32B 25/04 20130101; Y10T 428/24331
20150115; B32B 27/08 20130101; B32B 2307/584 20130101; B32B 2307/72
20130101; B32B 3/266 20130101; B32B 2250/02 20130101; B32B 7/12
20130101; Y10T 428/24322 20150115; B32B 15/18 20130101; B25B 11/005
20130101; B32B 2307/724 20130101; B32B 5/16 20130101; B32B 15/20
20130101; B32B 15/04 20130101; Y10T 428/24273 20150115; B32B 27/32
20130101; B32B 27/365 20130101; B32B 27/36 20130101; B32B 15/08
20130101; B32B 27/14 20130101; B32B 2307/558 20130101; B32B 27/302
20130101; H01L 21/6838 20130101; B32B 15/16 20130101 |
Class at
Publication: |
428/131 |
International
Class: |
B32B 3/10 20060101
B32B003/10 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 29, 2008 |
JP |
2008-250761 |
Claims
1. A suction sheet to be attached onto a suction surface of a
suction apparatus that holds an object by vacuum suction,
comprising: a substrate that has a plurality of through holes
formed therein and one surface to be brought into contact with the
suction surface, and a porous body with a thickness of 1.4 mm or
less that is adhered onto the other surface of the substrate so as
to cover the plurality of through holes.
2. The suction sheet according to claim 1, wherein the porous body
is made of ultrahigh molecular weight polyethylene.
3. The suction sheet according to claim 2, wherein the porous body
has been made porous by sintering ultrahigh molecular weight
polyethylene powder.
4. The suction sheet according to claim 1, wherein the plurality of
through holes are arranged so that the distance between the center
of each individual through hole and the center of its adjacent
through hole closest thereto is 65 mm or less.
5. The suction sheet according to claim 4, wherein the plurality of
through holes each have an opening area of 64 mm.sup.2 or less.
6. The suction sheet according to claim 5, wherein
B/A.sup.2.gtoreq.0.015 is satisfied, where a maximum length of
sides of a minimum rectangular frame that circumscribes a contour
of the through hole as viewed in an axis direction is referred to
as A, and a thickness of the porous body is referred to as B.
7. The suction sheet according to claim 1, wherein the substrate is
a plastic plate or a metal plate.
8. The suction sheet according to claim 1, wherein the suction
surface is provided with a recess for suction formed thereon, and
the plurality of through holes are provided within a region
corresponding to the recess with a size smaller than the
recess.
9. The suction sheet according to claim 8, wherein the recess is
formed by a plurality of grooves.
Description
TECHNICAL FIELD
[0001] The present invention relates to a suction sheet to be
mounted on a suction apparatus that holds an object by vacuum
suction.
BACKGROUND ART
[0002] Conventionally, a suction apparatus that holds an object by
vacuum suction has been used, for example, in a step for processing
a thin light sheet or film, such as metal foil, plastic film and
green sheet. Such a sheet or film is fixed or conveyed by this
suction apparatus. An air permeable porous sheet is adhered onto
the suction surface of the suction apparatus, for example, for
protection of the object (for example, see Patent Literature
1).
CITATION LIST
Patent Literature
[0003] Patent Literature 1: JP 2001-353788 A
SUMMARY OF INVENTION
Technical Problem
[0004] In the case where the object is a thin light sheet or film,
the surface shape of the porous sheet is transferred to the object
in the vacuum suction, and the transfer marks cause adverse effects
on the performance or appearance of the final product in some
cases. In order to prevent the formation of such transfer marks, it
is conceivable that the suction rate is reduced to decrease the
pressure difference caused by the vacuum drawing. However, in this
case, since a conventional porous sheet is comparatively thick (for
example, 2 mm in the example of Patent Literature 1), the air is
drawn also through the side surfaces of the porous sheet, resulting
in failure to obtain a sufficient suction force due to the
influence of the lateral leakage.
[0005] As a possible solution to this problem, the lateral leakage
may be reduced by use of a porous sheet with a reduced thickness.
In this way, it is possible to obtain a sufficient suction force
with a low suction rate. However, such a suction apparatus is
generally provided with a recess for suction formed on its suction
surface. Therefore, in the case of using the porous sheet with a
reduced thickness, the porous sheet is significantly deformed upon
the suction such that the sheet is drawn into the recess because of
its low rigidity. Thus, the edge of the recess on the suction
surface is strongly pressed against the object through the porous
sheet, which causes suction marks to be formed on the object.
[0006] In view of such circumstances, the present invention aims to
provide a suction sheet capable of reducing the lateral leakage and
suppressing the formation of suction marks on the object.
Solution to Problem
[0007] For achieving the aforementioned purpose, the present
invention provides a suction sheet to be attached onto a suction
surface of a suction apparatus that holds an object by vacuum
suction. The suction sheet is provided with: a substrate that has a
plurality of through holes formed therein and one surface to be
brought into contact with the suction surface; and a porous body
with a thickness of 1.4 mm or less that is adhered onto the other
surface of the substrate so as to cover the plurality of through
holes.
Advantageous Effects of Invention
[0008] According to the above-mentioned configuration, the porous
body is as thin as 1.4 mm or less. Thus, it is possible to reduce
air suction through the side surfaces of the porous body, that is,
the lateral leakage. Moreover, this porous body is adhered to the
substrate provided with through holes formed therein. Therefore, a
reduction in the size of the through holes leads to a reduction in
the deformation of the porous body, where the porous body deforms
such that it is drawn in the through holes due to suction. As a
result, it is possible to suppress the edges of the through holes
from being pressed against the object. Accordingly, the present
invention makes it possible to reduce the lateral leakage and
suppress the formation of suction marks on the object.
BRIEF DESCRIPTION OF DRAWINGS
[0009] FIG. 1 is a sectional view showing a state in which a
suction sheet according to one embodiment of the present invention
is attached onto the suction surface of a suction apparatus.
[0010] FIG. 2A is a sectional view taken along the line IIA-IIA in
FIG. 1, and FIG. 2B is a plan view showing a substrate.
DESCRIPTION OF EMBODIMENTS
[0011] Hereinafter, the best mode for carrying out the present
invention is described in detail with reference to the
drawings.
[0012] FIG. 1 shows a state in which a suction sheet 1 according to
one embodiment of the present invention is attached onto a suction
surface 4a of a suction apparatus 4. The suction apparatus 4 is
configured to convey an object while holding it by vacuum suction
and is provided with a suction head 40 shown in FIG. 1, a moving
mechanism (not shown) for moving the suction head 40 up and down, a
shifting mechanism (not shown) for shifting the suction head 40 in
the horizontal direction, and a vacuum pump (not shown) connected
to the suction head 40 through a suction path 41. Further, the
lower surface of the suction head 40 in parallel to the horizontal
plane serves as the suction surface 4a that allows the object to be
held thereon by suction. It should be noted that the suction sheet
1 can be mounted not only on the suction apparatus 4 that conveys
an object but also on another suction apparatus having a function
of holding an object by vacuum suction (for example, processing
apparatuses such as a polishing apparatus and a dicing apparatus)
in a wide range of applications.
[0013] On the suction surface 4a, a recess 42 for suction is
provided, and the suction path 41 opens on the bottom surface of
the recess 42. In this embodiment, the recess 42 is formed by one
transverse groove 42a extending toward both sides from the suction
path 41, and four longitudinal grooves 42b each extending toward
the other two sides from the transverse groove 42a, as shown in
FIG. 2A. The grooves 42a and 42b each have a width, for example, of
10 mm. However, the shape of the recess 42 is not limited to this,
and can be appropriately selected. For example, the recess 42 may
be formed by a groove in the form of a cross and a groove in the
form of a frame that surrounds this cross. Alternatively, the
recess 42 may be formed, for example, by a plurality of circular
bottomed holes arranged in the form of a matrix on the suction
surface 4a.
[0014] The suction sheet 1 has a size such that the suction sheet 1
can close the recess 42 (for example, a size approximately equal to
that of the suction surface 4a or slightly smaller than it). The
suction sheet 1 is fixed to the suction surface 4a, for example,
using double-sided adhesive tape. The suction sheet 1 is provided
with: a substrate 2 having one surface 2a (which is the upper
surface in FIG. 1) to be brought into contact with the suction
surface 4a and the other surface 2b (which is the lower surface in
FIG. 1); and a porous body 3 adhered onto the other surface 2b of
the substrate 2.
[0015] The substrate 2 needs only to have an appropriate rigidity
(for example, a rigidity modulus (modulus of transverse elasticity)
of about 1 MPa to 300 GPa), and the material thereof is not
particularly limited. For example, a plastic plate made of
polyethylene, polypropylene, polystyrene, polycarbonate,
polyethylene terephthalate etc., a metal plate made of stainless
steel, aluminium etc., or a rubber plate made of silicone rubber,
nitrile rubber, ethylene propylene rubber, urethane rubber, natural
rubber etc. can be used as the substrate 2. Further, the thickness
of the substrate 2, for example, is 0.3 to 30 mm in the case of a
plastic plate or rubber plate, and 0.2 to 20 mm in the case of a
metal plate.
[0016] In the substrate 2, a plurality of through holes 21
extending through the substrate 2 in the thickness direction
thereof are provided within a region corresponding to the recess
42, as shown in FIG. 2B. In this embodiment, the through holes 21
are provided only within the region corresponding to the recess 42.
However, the through holes 21 may be provided over the entire
surface of the substrate 2 in a regular or random pattern. In this
case, through holes in the other region that do not correspond to
the recess 42 are only to be closed by the suction surface 4a.
However, it is more preferable that the through holes 21 be formed
only within the region corresponding to the recess 42, as this
embodiment, in view of the processing efficiency and the
stabilization of the suction force during suction.
[0017] The through holes 21 are preferably arranged so that the
distance between the center of each individual through hole 21 and
the center of its adjacent through hole 21 closest thereto should
be 90 mm or less. In order to achieve this, the through holes 21
are arrayed on the center lines of all the grooves 42a and 42b with
a pitch of 10 mm that satisfies the above-mentioned condition of 90
mm or less, so that the distance between the centers of each
adjacent pair of through holes 21 is set to 10 mm, in this
embodiment. It should be noted that, in the case where the through
holes 21 are arranged in the form of a matrix, the row and column
pitch may be set to 90 mm or less as mentioned above. The distance
between the center of each individual through hole 21 and the
center of its adjacent through hole 21 closest thereto is more
preferably 65 mm or less.
[0018] The through holes 21 each are preferably provided with a
size smaller than the recess 42, that is, a size such that each
through hole 21 does not extend over the recess 42 in plan view.
Specifically in view of reducing the deformation of the porous body
3 during suction, each through hole 21 preferably has an opening
area (cross-sectional area in a direction orthogonal to the axis
direction) of 64 mm.sup.2 or less (for example, with each side of 8
mm or less in the case of the through hole 21 in a square shape,
and with a diameter of about 9 mm or less in the case of the
through hole 21 in a circular shape), more preferably has an
opening area of 30 mm.sup.2 or less. Furthermore, each through hole
21 preferably has a size equal to or larger than a circle with a
diameter of 0.5 mm, more preferably has a size equal to or larger
than a circle with a diameter of 1.0 mm, most preferably has a size
equal to or larger than a circle with a diameter of 1.5 mm so that
the air can flow through the through holes 21 smoothly even when
the suction rate of the suction apparatus 4 is decreased. Further,
each through hole 21 may have a rectangular, ellipsoidal shape or
the like, as viewed in the axis direction. However, it preferably
has a circular shape in view of workability.
[0019] The porous body 3 is adhered onto the other surface 2b of
the substrate 2 so as to cover all the through holes 21. The porous
body 3 needs only to be in the form of a porous sheet. Examples
thereof include woven fabrics, nonwoven fabrics, a perforated film
and a sintered sheet body that has been made porous by sintering
plastic powder. Above all, the sintered sheet body of plastic
powder is preferably used, in view that the problem of deposition
of foreign matters on the object due to fallen fibers, etc. can be
prevented, and the holes are present uniformly over the entire
surface so that it is easy to obtain a uniform suction force over
the entire surface. Furthermore, since friction occurs between the
porous body 3 and the object in use, a sintered sheet body produced
using ultrahigh molecular weight polyethylene powder with an
average molecular weight of at least 500,000 is preferable in view
of its excellent abrasion resistance and impact resistance.
[0020] In order to produce such a sintered sheet body using
ultrahigh molecular weight polyethylene powder, the following
methods, etc. are available. The first method is a method in which
a sintered block is produced by sintering the powder put into a
mold, and then the sintered block is formed into a sheet by lathe
turning. The second method is a method in which the powder is
sintered in a state where the powder is spread to a specific
thickness. The third method is a method in which a so-called slurry
obtained by dispersing the powder in a solvent is applied, to a
specific thickness, onto a metal plate with the surface subjected
to mold release treatment, and then it is heated to the melting
point or more of ultrahigh molecular weight polyethylene so as to
be sintered.
[0021] The thickness of the porous body 3 is preferably at least
0.05 mm but not more than 1.4 mm. This is because the thickness
less than 0.05 mm makes adverse effects, such as a damage of the
porous body 3, likely to occur, whereas the thickness exceeding 1.4
mm makes air suction through the side surfaces of the porous body
3, so-called lateral leakage, significant, though the bending
elastic modulus of the porous body 3 differs depending on the
production method, etc., and accordingly the degree of the
deformation during suction differs due to this. The thickness of
the porous body 3 is more preferably at least 0.05 mm but not more
than 1.0 mm.
[0022] The air permeability of the porous body 3 is preferably at
least 0.1 cm.sup.3/cm.sup.2/s but not more than 300
cm.sup.3/cm.sup.2/s, in terms of Frazier Number. The Frazier Number
herein means a numerical value measured using a Frazier air
permeability tester prescribed in JIS L 1096. The air permeability
is more preferably at least 0.5 cm.sup.3/cm.sup.2/s but not more
than 100 cm.sup.3/cm.sup.2/s.
[0023] Furthermore, the relationship between the size of the
through hole 21 in the substrate 2 and the thickness of the porous
body 3 preferably satisfies B/A.sup.2.gtoreq.0.015, where the
maximum length of the sides of the minimum rectangular frame that
circumscribes the contour of the through hole 21 as viewed in the
axis direction is referred to as A, and the thickness of the porous
body 3 is referred to as B, under the condition that the thickness
of the porous body 3 falls within the range of 0.05 to 1.4 mm as
mentioned above. In the case where the through hole 21 is circular,
A is equal to the diameter of the through hole 21. The B/A.sup.2
less than 0.015 might cause the porous body 3 to deform
significantly due to suction, though it depends also on the
material or structure of the porous body 3. The B/A.sup.2 is more
preferably at least 0.025, most preferably 0.025 to 0.040, under
the condition that the thickness of the porous body 3 falls within
the range of 0.05 to 1.4 mm.
[0024] The method for bonding the porous body 3 to the substrate 2
is not particularly limited as long as it is a method that does not
cause the through holes 21 and the voids inside the porous body 3
to be closed, and ensures the air flow through the through holes
21. For example, heat fusion, heat welding with a hot melt sheet,
adhesion with a double-sided adhesive tape or adhesive agent can be
used therefor. In the case of using an adhesive agent, it is
possible to ensure air permeability by forming spaces where the
adhesive agent is locally absent such that it is in a porous state,
even if adhesive agent is applied onto the entire surface of the
porous body 3. Alternatively; it also is possible that, while the
size of the porous body 3 is set to the extent that the porous body
3 extends over the substrate 2, the extending portion is bent over
the edges of the substrate 2 so as to be fixed onto the side
surfaces of the substrate 2 with an adhesive tape, adhesive agent,
etc.
[0025] According to the adhesive sheet 1 having the above-described
configuration, it is possible to reduce air suction through the
side surfaces of the porous body 3, that is, so-called lateral
leakage, by use of the porous body 3 that is as thin as 1.4 mm or
less. Moreover, this porous body 3 is adhered to the substrate 2
provided with through holes 21 formed therein. Therefore, a
reduction in the size of the through holes 21 leads to a reduction
in the deformation of the porous body 3, where the porous body 3
deforms such that it is drawn in the through holes 21 due to
suction. As a result, it is possible to suppress the edges of the
through holes 21 from being pressed against the object. This makes
it possible to suppress the formation of suction marks on the
object.
EXAMPLES
[0026] Hereinafter, the present invention is described in detail
with reference to examples. However, the present invention is not
restricted by these examples at all.
Examples
[0027] A mold with an internal diameter of 500 mm and a height of
500 mm was filled with ultrahigh molecular weight polyethylene
powder (with a molecular weight of 5,000,000, a bulk density of
0.47 g/cm.sup.3 and an average particle size of 120 .mu.m). This
was put in a metal pressure vessel, and then the pressure inside
the vessel was reduced to 10 hPa. Thereafter, the inside of the
vessel was adjusted to 160.degree. C. and 6080 hPa by introducing
heated water vapor into the vessel, which was heated for 5 hours
and then slowly cooled. Thus, a cylindrical sintered block was
obtained. This sintered block was cut into sintered sheet bodies
with various thickness by lathe turning, each of which was cut into
a 100 mm square. These sintered sheet bodies were pressed at
130.degree. C. and 30 Pa for 1 hour by a press machine, so that
porous bodies with a thickness varying from 0.025 to 1.0 mm were
produced.
[0028] For each porous body, the bulk density was calculated from
its volume and weight, and the porosity was calculated by the
formula {1-(bulk density/true density)}.times.100, taking the true
density of the ultrahigh molecular weight polyethylene as 0.935
g/cm.sup.3,
[0029] 2 mm thick and 100 mm square polyethylene plates or
aluminium plates were prepared, and circular through holes with a
diameter varying from 1.5 to 6.0 mm were formed therethrough as
shown in FIG. 2B. Thus, a plurality of types of substrates were
produced. The porous bodies were adhered respectively to the
substrates. Thus, suction sheets were obtained (Examples 1 to
8).
[0030] The porous bodies were bonded to the substrates with a
double-sided adhesive tape (No. 5606: manufactured by NITTO DENKO
CORPORATION) that used PET as a base material. The double-sided
adhesive tape was adhered onto the entire surface of each
polyethylene plate or aluminium plate before perforation, and then
the plate was perforated over the double-sided adhesive tape so
that the closure of the through holes by the double-sided adhesive
tape was avoided.
Comparative Example
[0031] A 1.5 mm thick porous body was produced in the same manner
as in the examples except that the thickness of the sintered sheet
body to be cut out from the sintered block was increased. This was
adhered to a substrate (polyethylene plate) in which through holes
each having a diameter of 6.0 mm are provided, in the same manner
as in the examples. Thus, a suction sheet was obtained. The
porosity of the porous body was calculated in the same manner as in
the examples,
[0032] Evaluation
[0033] For each of the suction sheets of Examples 1 to 8 and
Comparative Example, the B/A.sup.2 was calculated from the
thickness B of the porous body and the diameter A of each through
hole in the substrate.
[0034] Further, the suction sheet was mounted on a suction
apparatus having a conveying function, which was subjected to a
suction test using an aluminium foil with a thickness of 10 .mu.m.
As the suction test, the suction rate was set to 10 L/min, a cyclic
series of the suction, conveying and detachment of the aluminium
foil was repeated 100 times between two tables, out of which the
number of suction failure was counted. Further, the surface of the
aluminium foil after the test was observed, and the presence or
absence of suction marks remaining thereon was checked by visual
inspection.
[0035] Table 1 shows the specification data, the B/A.sup.2 and the
test results for each suction sheet.
TABLE-US-00001 TABLE 1 Substrate Porous body Hole Suction test
Thickness Poro- Base diameter The number Status of B sity mate- A
of suction suction (mm) (%) rial (mm) B/A.sup.2 failure marks EX. 1
0.3 29 PE plate 3.0 0.033 0 .smallcircle. EX. 2 0.32 29 PE plate
4.5 0.016 0 .smallcircle. EX. 3 0.05 32 PE plate 1.5 0.022 0
.smallcircle. EX. 4 1.0 27 PE plate 6.0 0.028 0 .smallcircle. EX. 5
0.3 29 Al plate 3.0 0.033 0 .smallcircle. EX. 6 0.3 29 PE plate 6.0
0.008 0 .DELTA. EX. 7 0.025 33 PE plate 1.5 0.011 0 .DELTA. EX. 8
1.0 27 PE plate 1.5 0.444 1 .smallcircle. C.EX. 1.5 27 PE plate 6.0
0.042 6 .smallcircle.
[0036] In the column of the table that indicates the status of
suction marks, .smallcircle. represents a good status, and .DELTA.
represents a status where a few suction marks were left.
[0037] It can be seen from Table 1 that the conveyance of the
aluminium foil was well carried out in general in Examples 1 to 8
(particularly well in Examples 1 to 7), though a few suction marks
were left in Examples 6 and 7 having a B/A.sup.2 of less than
0.015. In Examples 2 and 3 having a B/A.sup.2 of less than 0.025, a
slight deformation of the aluminium foil, but not so far as to be
recognized as suction marks, was observed. In contrast, in
Comparative Example with the porous body having a thickness
exceeding 1.4 mm, a sufficient suction force was not obtained and
problematic suction failures occurred, as already described in the
section of Technical problem.
* * * * *